Printed matter needs to be printed with a high level of quality to ensure readability by automation equipment, especially when old technology readers require very high print contrast ratios to ensure readability. The problem is particularly evident when barcodes are automatically read by postal automation equipment and other barcode readers.
Barcodes have been used in a wide variety of applications as a source for information. Typically barcodes are used at a point-of-sale terminal in merchandising for pricing and inventory control. Barcodes are also used in controlling personnel access systems, mailing systems, and in manufacturing for work-in process and inventory control systems, etc. The barcodes themselves represent numbers or alphanumeric characters by series of adjacent stripes of various widths, (i.e. a width modulated universal product code), heights (i.e. a height modulated POSTNET barcode), or position (2D barcode).
An ordinary barcode is a set of binary numbers. It typically consists of black bars and white spaces. A wide black bar space may signify a one and a thin black bar or space may signify a zero. The binary numbers stand for decimal numbers or letters. There are several different kinds of barcodes. In each one, a number, letter or other character is formed by a pre-established number of bars and spaces.
Width modulated barcodes are “vertically redundant”, meaning that the same information is repeated vertically. They are in fact a one-dimensional code. The heights of the bars can be truncated without any lose of information. A two-dimensional code stores information along the height as well as the length of the symbol. Thus, in the same area more information may be stored in a two dimensional barcode than in a one dimensional barcode.
Current technology printers may leave small unintended voids between pixels which prevent achievement of the highest print contrast and uniform coverage of which the ink dyes or pigments are theoretically capable of. Such unintended voids are caused by the nature of ink jet printing of placing small drops (1-50 pL) on rough surface of paper with “peaks and valleys”. The ink jet drops do not reach the paper surface in a uniform way and therefore cause to “graininess” as defined by the Standard ISO 13660, herein incorporated by reference, or non uniform print coverage especially on plain paper. Therefore the result is a degradation of the print quality of printed images. In comparison the mass thermal transfer printing achieves a uniform print coverage with the melt wax bridging the irregularities of the paper surface.
These characteristics affect the uniformity of the modules printed in the 2 D bar codes which might be interpreted as background by scanners. Barcodes, are also very sensitive to ink in unwanted locations—the line of contact and the white spaces in barcodes must be preserved and readability can be severely impacted if ink is allowed to bleed into regions which are intended to be blank (print growth).
One of the problems of the prior art is that it is often difficult to automatically read printed information.
Another problem of the prior art is that s often difficult to automatically read printed information that has a low print contrast ratio which is due to non optimal print coverage.